<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>POST请求</title>
    <style>
        #result{
            width: 200px;
            height: 100px;
            border: solid 1px #90b;
        }
    </style>
</head>
<body>
    <div id="result"></div>
    <script>
        const result = document.getElementById('result');
        result.addEventListener("mouseover",function(){
            const xhr = new XMLHttpRequest();
            //设置超时
            xhr.timeout = 2000;
            xhr.ontimeout = function(){
                alert("网络异常，请稍后重试！")
            }
            xhr.onerror = function(){
                alert("你的网络似乎出现一些问题")
            }
            xhr.open('POST','http://127.0.0.1:8080/server');
            //设置请求头
            xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
            xhr.send();
            xhr.onreadystatechange = function(){
                if(xhr.readyState === 4){
                    if(xhr.status >=200 && xhr.status<300){
                        result.innerHTML = xhr.response;
                    }
                }
            }
        })
    </script>
</body>
</html>